Continuous glass strands are typically chopped into particulate glass strands for use in reinforcing plastics and the like by passing the strands between a pair of rollers. One of these rollers includes a plurality of cutting blades spaced around its circumference. The other roller, known as a back-up or cot roll, provides an annular cutting surface such that the blades cut through the glass strand and into the back-up surface. Typical of such a chopping operation is U.S. Pat. No. 3,869,268, which is assigned to the assignee of the present invention and which is incorporated herein by reference.
As disclosed in the aforementioned patent, the back-up or cot roll has as its face an annular cutting surface or ring formed of a resilient material such as natural or synthetic rubber, polyurethanes and the like. The surface of this ring has a Shore A hardness preferably of about 50 to 90. In actuality, the surface is a ring or donut of the resilient material which surrounds a metal wheel and which is enclosed by face plates on the sides of the wheel.
As the cutting blades chop the strand and gouge into the cutting surface, the cutting surface quickly deteriorates. Thus, for example, these rings must be replaced at a rate of about once every two to eight hours, depending upon the individual wear for a given surface and the amount of downtime for a given chopper. Since the ring or donut must both sit firmly on the wheel and must provide for a proper degree of contact or mesh with the chopping blades, both the inner and outer diameters of the ring are critical. Thus, if the inner diameter of the ring is too large or too small, it will not fit properly on the wheel and must be discarded. In addition, if the outer diameter does not properly mesh with the cutting blades, glass strand will not be chopped properly. Because of this second problem, it has been impossible in the past to resurface used rings to increase the total life of the rings and thus decrease the cost of cutting rings for the chopper.
For example, it has been found that proper cutting of the strands may be accomplished when the cot roll and the cutting wheel surface, from which the blades extend, are in contact or spaced up to the length of the projection of the blades from the cutting wheel surface.
It is thus a primary objective of the present invention to enable cutting rings having heretofore unusable inner and outer diameters to be employed in the chopping of glass strands.
It is also a primary objective of the present invention to increase the life of the rings by decreasing their rate of wear and by enabling resurfacing and reuse of the rings.
It is a further objective of the present invention to provide for a smoother operation of the chopping system.